Musannaf Ibn Abi Shayba 3:3654

Muhammad ibn Abi ‘Adi narrated to us, from Ibn ‘Awn, who said: I said to Muhammad [ibn Sirin], "A man moves forward to the row in prayer." He said, "I do not see any harm in him moving forward a step or two." And he said regarding the one who prays [while] standing across the row, "I do not know what that is."